NAME
Catalyst::Plugin::Cache - Flexible caching support for Catalyst.
SYNOPSIS
use Catalyst qw/
Cache
/;
# configure a backend or use a store plugin
__PACKAGE__->config->{cache}{backend} = {
class => "Cache::Bounded",
# ... params ...
};
# In a controller:
sub foo : Local {
my ( $self, $c, $id ) = @_;
my $cache = $c->cache;
my $result;
unless ( $result = $cache->get( $id ) ) {
# ... calculate result ...
$c->cache->set( $id, $result );
}
};
DESCRIPTION
This plugin gives you access to a variety of systems for caching data.
It allows you to use a very simple configuration API, while maintaining
the possibility of flexibility when you need it later.
Among its features are support for multiple backends, segmentation based
on component or controller, keyspace partitioning, and so more, in
various subsidiary plugins.
METHODS
cache $profile_name
cache %meta
Return a curried object with metadata from $profile_name or as
explicitly specified.
If a profile by the name $profile_name doesn't exist, but a backend
object by that name does exist, the backend will be returned
instead, since the interface for curried caches and backends is
almost identical.
This method can also be called without arguments, in which case is
treated as though the %meta hash was empty.
See "METADATA" for details.
curry_cache %meta
Return a Catalyst::Plugin::Cache::Curried object, curried with
%meta.
See "METADATA" for details.
cache_set $key, $value, %meta
cache_get $key, %meta
cache_remove $key, %meta
These cache operations will call choose_cache_backend with %meta,
and then call "set", "get", or "remove" on the resulting backend
object.
choose_cache_backend %meta
Select a backend object. This should return undef if no specific
backend was selected - its caller will handle getting
"default_cache_backend" on its own.
This method is typically used by plugins.
get_cache_backend $name
Get a backend object by name.
default_cache_backend
Return the default backend object.
temporary_cache_backend
When no default cache backend is configured this method might return
a backend known to work well with the current Catalyst::Engine. This
is a stub.
METADATA
Introduction
Whenever you set or retrieve a key you may specify additional metadata
that will be used to select a specific backend.
This metadata is very freeform, and the only key that has any meaning by
default is the "backend" key which can be used to explicitly choose a
backend by name.
The "choose_cache_backend" method can be overridden in order to
facilitate more intelligent backend selection. For example,
Catalyst::Plugin::Cache::Choose::KeyRegexes overrides that method to
select a backend based on key regexes.
Another example is a Catalyst::Plugin::Cache::ControllerNamespacing,
which wraps backends in objects that perform key mangling, in order to
keep caches namespaced per controller.
However, this is generally left as a hook for larger, more complex
applications. Most configurations should make due XXXX
The simplest way to dynamically select a backend is based on the "Cache
Profiles" configuration.
Meta Data Keys
"choose_cache_backend" is called with some default keys.
key Supplied by "cache_get", "cache_set", and "cache_remove".
value
Supplied by "cache_set".
caller
The package name of the innermost caller that doesn't match
"qr/Plugin::Cache/".
caller_frame
The entire "caller($i)" frame of "caller".
component
The package name of the innermost caller who "isa"
Catalyst::Component.
component_frame
This entire "caller($i)" frame of "component".
controller
The package name of the innermost caller who "isa"
Catalyst::Controller.
controller_frame
This entire "caller($i)" frame of "controller".
Metadata Currying
In order to avoid specifying %meta over and over again you may call
"cache" or "curry_cache" with %meta once, and get back a curried cache
object. This object responds to the methods "get", "set", and "remove",
by appending its captured metadata and delegating them to "cache_get",
"cache_set", and "cache_remove".
This is simpler than it sounds.
Here is an example using currying:
my $cache = $c->cache( %meta ); # cache is curried
$cache->set( $key, $value );
$cache->get( $key );
And here is an example without using currying:
$c->cache_set( $key, $value, %meta );
$c->cache_get( $key, %meta );
See Catalyst::Plugin::Cache::Curried for details.
CONFIGURATION
$c->config->{cache} = {
...
};
All configuration parameters should be provided in a hash reference
under the "cache" key in the "config" hash.
Backend Configuration
Configuring backend objects is done by adding hash entries under the
"backends" key in the main config.
A special case is that the hash key under the "backend" (singular) key
of the main config is assumed to be the backend named "default".
class
Instantiate a backend from a Cache compatible class. E.g.
$c->config->{cache}{backends}{small_things} = {
class => "Cache::Bounded",
interval => 1000,
size => 10000,
};
$c->config->{cache}{backends}{large_things} = {
class => "Cache::Memcached::Managed",
data => '1.2.3.4:1234',
};
The options in the hash are passed to the class's "new" method.
The class will be "required" as necessary during setup time.
store
Instantiate a backend using a store plugin, e.g.
$c->config->{cache}{backend} = {
store => "FastMmap",
};
Store plugins typically require less configuration because they are
specialized for Catalyst applications. For example
Catalyst::Plugin::Cache::Store::FastMmap will specify a default
"share_file", and additionally use a subclass of Cache::FastMmap
that can also store non reference data.
The store plugin must be loaded.
Cache Profiles
profiles
Supply your own predefined profiles for cache metadata, when using
the "cache" method.
For example when you specify
$c->config->{cache}{profiles}{thumbnails} = {
backend => "large_things",
};
And then get a cache object like this:
$c->cache("thumbnails");
It is the same as if you had done:
$c->cache( backend => "large_things" );
Miscellaneous Configuration
default_store
When you do not specify a "store" parameter in the backend
configuration this one will be used instead. This configuration
parameter is not necessary if only one store plugin is loaded.
TERMINOLOGY
backend
An object that responds to the methods detailed in
Catalyst::Plugin::Cache::Backend (or more).
store
A plugin that provides backends of a certain type. This is a bit
like a factory.
cache
Stored key/value pairs of data for easy re-access.
metadata
"Extra" information about the item being stored, which can be used
to locate an appropriate backend.
curried cache
my $cache = $c->cache(type => 'thumbnails');
$cache->set('pic01', $thumbnaildata);
A cache which has been pre-configured with a particular set of
namespacing data. In the example the cache returned could be one
specifically tuned for storing thumbnails.
An object that responds to "get", "set", and "remove", and will
automatically add metadata to calls to "$c->cache_get", etc.
SEE ALSO
Cache - the generic cache API on CPAN.
Catalyst::Plugin::Cache::Store - how to write a store plugin.
Catalyst::Plugin::Cache::Curried - the interface for curried caches.
Catalyst::Plugin::Cache::Choose::KeyRegexes - choose a backend based on
regex matching on the keys. Can be used to partition the keyspace.
Catalyst::Plugin::Cache::ControllerNamespacing - wrap backend objects in
a name mangler so that every controller gets its own keyspace.
AUTHOR
Yuval Kogman, "nothingmuch@woobling.org"
COPYRIGHT & LICENSE
Copyright (c) Yuval Kogman, 2006. All rights reserved.
This library is free software, you can redistribute it and/or modify it
under the same terms as Perl itself, as well as under the terms of the
MIT license.